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MachOImageSymbolTableReader: permit indirect symbols to exist among

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external defined symbols.

Indirect symbols remain unsupported.

Xcode 5.1 ld64-236.3/src/ld/LinkEditClassic.hpp
ld::tool::SymbolTableAtom<>::addGlobal() is responsible for producing
symbols found in the extdef portion of the symbol table. It always sets
the type to N_ABS, N_SECT, or N_INDR, each with the N_EXT bit set. The
N_PEXT bit is never set for non-object files, and we’re not concerned
with reading object files. With this change to tolerate N_INDR, I think
we’re covering all of the symbol types that we might find ld writing to
the extdef portion of the symbol table.

https://groups.google.com/a/chromium.org/forum/#!topic/crashpad-dev/k7QkLwO71Zo

R=rsesek@chromium.org

Review URL: https://codereview.chromium.org/901463004
This commit is contained in:
Mark Mentovai 2015-02-05 13:39:20 -05:00
parent b7d214e741
commit 878400947f
2 changed files with 60 additions and 50 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
snapshot/mac/mach_o_image_reader_test.cc
View File

@ -393,14 +393,8 @@ void ExpectSymbol(const Nlist* entry,
uint32_t entry_type = entry->n_type & N_TYPE;
if ((entry->n_type & N_STAB) == 0 && (entry->n_type & N_PEXT) == 0 &&
entry_type != N_UNDF && entry_type != N_PBUD &&
(entry_type == N_ABS || entry_type == N_SECT) &&
(entry->n_type & N_EXT) == 1) {
// Note that this catches more symbols than MachOImageSymbolTableReader
// does. This test looks for all external defined symbols, but the
// implementation excludes indirect (N_INDR) symbols. This is intentional,
// because indirect symbols are currently not seen in the wild, but if they
// begin to be used more widely, this test is expected to catch them so that
// a decision can be made regarding whether support ought to be implemented.
mach_vm_address_t actual_address;
ASSERT_TRUE(
actual_image->LookUpExternalDefinedSymbol(name, &actual_address));

102
snapshot/mac/mach_o_image_symbol_table_reader.cc
View File

@ -111,58 +111,74 @@ class MachOImageSymbolTableReaderInitializer {
std::string symbol_info = base::StringPrintf(", symbol index %zu%s",
skip_count + symbol_index,
module_info_.c_str());
uint8_t symbol_type = symbol.n_type & N_TYPE;
bool valid_symbol = true;
if ((symbol.n_type & N_STAB) == 0 && (symbol.n_type & N_PEXT) == 0 &&
(symbol_type == N_ABS || symbol_type == N_SECT) &&
(symbol.n_type & N_EXT)) {
if (symbol.n_strx >= strtab_size) {
LOG(WARNING) << base::StringPrintf(
"string at 0x%x out of bounds (0x%llx)",
symbol.n_strx,
strtab_size) << symbol_info;
return false;
}
if (!string_table) {
string_table = process_reader_->Memory()->ReadMapped(
strtab_address, strtab_size);
if (!string_table) {
LOG(WARNING) << "could not read string table" << module_info_;
uint8_t symbol_type = symbol.n_type & N_TYPE;
if (symbol_type == N_ABS || symbol_type == N_SECT) {
if (symbol.n_strx >= strtab_size) {
LOG(WARNING) << base::StringPrintf(
"string at 0x%x out of bounds (0x%llx)",
symbol.n_strx,
strtab_size) << symbol_info;
return false;
}
}
std::string name;
if (!string_table->ReadCString(symbol.n_strx, &name)) {
LOG(WARNING) << "could not read string" << symbol_info;
return false;
}
if (!string_table) {
string_table = process_reader_->Memory()->ReadMapped(
strtab_address, strtab_size);
if (!string_table) {
LOG(WARNING) << "could not read string table" << module_info_;
return false;
}
}
if (symbol_type == N_ABS && symbol.n_sect != NO_SECT) {
LOG(WARNING) << base::StringPrintf("N_ABS symbol %s in section %u",
name.c_str(),
symbol.n_sect) << symbol_info;
return false;
}
std::string name;
if (!string_table->ReadCString(symbol.n_strx, &name)) {
LOG(WARNING) << "could not read string" << symbol_info;
return false;
}
if (symbol_type == N_SECT && symbol.n_sect == NO_SECT) {
LOG(WARNING) << base::StringPrintf(
"N_SECT symbol %s in section NO_SECT",
name.c_str()) << symbol_info;
return false;
}
if (symbol_type == N_ABS && symbol.n_sect != NO_SECT) {
LOG(WARNING) << base::StringPrintf("N_ABS symbol %s in section %u",
name.c_str(),
symbol.n_sect) << symbol_info;
return false;
}
if (external_defined_symbols->count(name)) {
LOG(WARNING) << "duplicate symbol " << name << symbol_info;
return false;
}
if (symbol_type == N_SECT && symbol.n_sect == NO_SECT) {
LOG(WARNING) << base::StringPrintf(
"N_SECT symbol %s in section NO_SECT",
name.c_str()) << symbol_info;
return false;
}
MachOImageSymbolTableReader::SymbolInformation symbol_info;
symbol_info.value = symbol.n_value;
symbol_info.section = symbol.n_sect;
(*external_defined_symbols)[name] = symbol_info;
} else if (dysymtab_command) {
LOG(WARNING) << "non-external symbol in extdefsym" << symbol_info;
if (external_defined_symbols->count(name)) {
LOG(WARNING) << "duplicate symbol " << name << symbol_info;
return false;
}
MachOImageSymbolTableReader::SymbolInformation this_symbol_info;
this_symbol_info.value = symbol.n_value;
this_symbol_info.section = symbol.n_sect;
(*external_defined_symbols)[name] = this_symbol_info;
} else {
// External indirect symbols may be found in the portion of the symbol
// table used for external symbols as opposed to indirect symbols when
// the indirect symbols are also external. These can be produced by
// Xcode 5.1 ld64-236.3/src/ld/LinkEditClassic.hpp
// ld::tool::SymbolTableAtom<>::addGlobal(). Indirect symbols are not
// currently supported by this symbol table reader, so ignore them
// without failing or logging a message when encountering them. See
// https://groups.google.com/a/chromium.org/d/topic/crashpad-dev/k7QkLwO71Zo
valid_symbol = symbol_type == N_INDR;
}
} else {
valid_symbol = false;
}
if (!valid_symbol && dysymtab_command) {
LOG(WARNING) << "non-external symbol with type " << symbol.n_type
<< " in extdefsym" << symbol_info;
return false;
}
}